C.
Variable Hydraulic Unit
(1)
The variable hydraulic unit consists of a cylinder block, reciprocating pistons, a variable angle wobbler, and a control piston. The variable unit is connected to the engine by direct gearing; consequently, the speed of the cylinder block is always proportional to the input speed and rotation is always in the same direction.
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24-11-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
VARIABLE
OVERDRIVE ANGLE UNDERDRIVE
VARIABLE UNIT
WOBBLER HYDRALIC PHASE HYDRALIC
PHASE
(MOTORING)
UNIT (PUMPING)RECIPROCATING
VARIABLE UNIT UNIT
RECIPROCATINGPISTONS
PISTONS
PORT PLATE (STATIONARY)
PORT PLATE (STATIONARY)LOW PRESSURE OIL
LOW PRESSURE OIL
FIXED UNIT
FIXED UNIT(MOTORING) (PUMPING)
CYLINDERBLOCK
CYLINDERBLOCK
CONTROLPISTON
CONTROLHIGH
CONTROL
PISTON PRESSURE
CYLINDER
EPICYCLIC EPICYCLIC
HIGH CONTROL
OIL GEAR GEAR
PRESSURE CYLINDER
UNIT UNIT
OIL
GEARED
DIFFERENTIAL
OUTPUT OUTPUT RING RING GEAR
GEAR CARRIER
OUTPUT
CARRIER SHAFTGEAR
SHAFT OUTPUTGEAR
PLANET GEAR
PLANET GEARS
INPUT
RING
GEAR
INPUT
RING
GEAR TO PUMPSTO PUMPS AND GOVERNOR
AND GOVERNOR INPUTGEAR
INPUT
GEAR
TO AIRCRAFTENGINE
CSD Gear Differential and Hydraulic Unit Schematic
Figure 3
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. CONSTANT SPEED DRIVES ú
24-11-00
ú CONFIG 1 ú 01 Page 6 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
(2)
When the transmission is in overdrive, the variable hydraulic unit will function as a hydraulic pump. To enable the variable unit to pump oil, the governor ports control oil to the control piston which in turn positions the wobbler so oil will be compressed as the pistons are forced into the rotating cylinder block. This high pressure (working pressure) oil is ported to the fixed hydraulic unit.
(3)
As the input speed increases and the need to add speed decreases, the governor will port less oil to the control cylinder until the variable wobbler is in a position approximately normal to the pistons. When the face of the variable wobbler is approximately perpendicular to the pistons, no oil (except that required to provide for power losses due to leakage) is pumped or received by the variable unit. At this time the transmission is in straight through drive.
(4)
When the transmission is operating in underdrive, the variable hydraulic unit will function as a motor. To enable the variable unit to operate as a motor (receive oil from the pumping unit), the governor ports oil away from the control cylinder causing the wobbler to be positioned so the volume for accommodating oil in the piston bores on the high pressure side is increased; consequently, oil flows from the fixed hydraulic unit to the variable unit.
D.
Fixed Hydraulic Unit
(1)
The fixed hydraulic unit consists of a cylinder block, reciprocating piston and a fixed angle wobbler. The direction of rotation and speed of the fixed hydraulic unit is determined by the volume of oil pumped or received by the variable hydraulic unit. This volume of oil is determined by the angular position of the variable wobbler and the speed of the variable block.
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